• Bulletin of the Korean Chemical Society
• /
• v.8 no.1
• /
• pp.31-39
• /
• 1987

By using a complete rate constant($k_e$) which treats a solvent (water) as a reactant, and a conventional rate constant($k_c$), which ignores the solvent in describing the rate, the parameters ${\Delta}V^{\neq}_s,\;{\Delta}H^{\neq}_s\;and\;{\Delta}S^{\neq}_s$ were introduced. These quantities represent the volume change, the enthalpy change, and the entropy change accompanying the electrostriction which occurs when solvent molecules condense on the activated complex. The authors measured the rates of the solvolysis of benzoyl chloride in water-acetone mixtures at $15^{\circ}$ to $30^{\circ}C$ and 1 bar to 2500 bars. Applying the authors' theory to the experimental results, the parameters, ${\Delta}V^{\neq}_s,\;{\Delta}H^{\neq}_s\;and\;{\Delta}S^{\neq}_s$ were evaluated, and it was found that they are all negative, indicating that water dipoles condense on the activated complex. They also proposed the following equations: ${\Delta}H^{\neq}_c\;=\;{\Delta}H^{\neq}_e\;+\;{\Delta}H^{\neq}_s\;and\; {\Delta}S^{\neq}_c\;=\;{\Delta}S^{\neq}_e\;+{\Delta}S^{\neq}_s\;,\;where\;{\Delta}H^{\neq}_c\;and\;{\Delta}H^{\neq}_c\;and\;{\Delta}S^{\neq}_s $are the activation enthalpy change and the activation entropy change for the conventional reaction rate, respectively, and ${\Delta}H^{\neq}_e$ and ${\Delta}S^{\neq}_e$ are the corresponding quantities for the complete reaction rate. The authors proposed that for the $SN_1$ type, all the quantities, ${\Delta}V^{\neq}_s,\;{\Delta}S^{\neq}_s\;,{\Delta}H^{\neq}_s\;and\;{\Delta}S^{\neq}_s$ are comparatively large, and for the $SN_2$ type, these quantities are smaller than for the $SN_1$ type, and occasionally the case ${\Delta}S^{\neq}_e$ < 0 occurs. Using these criteria, the authors concluded that at high temperature, high pressure and for a high water content solvent, the SN_1$ type mechanism predominates whereas in the reversed case the $SN_2$M type predominates.

• Journal of environmental and Sanitary engineering
• /
• v.16 no.3
• /
• pp.22-27
• /
• 2001

It have been investigated how algal and bacterial symbiotic reaction influences on removal of organic carbon in river ecosystem. And artificial experimentation apparatus was made for algae'and bacteia'culture as lab scale. Investigating and researching minutely the change of concentration of organic carbon substrate and the change of population density of algae'and of bacteria'with this artificial experimentation apparatus, the next results could be obtained. 1. Successful decrease of DOC(dissolved organic carbon) could not be expected unless algal and bacterial biomass floe was nut formed effectively and unless biosorption was not proceeded effectively in the very culture system in which artificial synthetic wastewater was supplied continuously at constant rate. 2. In conditions of culture liquid of 1335 glucnse mg/L(type 1) and of 267 glucose mg:L(type 2), the algal dominant species was always Chlorella vulgaris in both types in which artificial synthetic wastewater were supplied continuously at constant rate and algae population density was around maximum 107 cells/mL. 3. It was around 108 ~ 107 cells/mL that the population density of heterotrophic bacterium. In culture medium systems type 1 and type 2 in which artificial wastewater were supplied continuously at constant rate, the same density appeared initially when using the population density of Escherichia coli w 3110 as indirect indicator. And this density decreased rapidly till the culturing date 35 days were passed away, while this density increased with gentle slope after same date and then the trend of change at type 2 was more severe than one at type 1. 4. When seeing such a change of population density of Escherichia coli w 3110, the growth of heterotrophic bacterium appeared as survival instinct pattern of broader requirement of nutrient at condition of low concentration of organic carbon substrate than condition of high concentration of same substrate.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.58 no.12
• /
• pp.2505-2510
• /
• 2009

Semiconductor processes need measurement to confirm where there are problems in quality after progresses manufacturing process. This paper suggests equipment and automatic measure sampling method that control monitoring ratio according to change point occurrence availability of process that is not measure method by the existent simple ratio rate. This paper defines measure section as ailment section, metastable section and stability section by change point standard and create statistical model of each section and developed suitable measure rate model by section. As a result, we have accomplished maximum throughput and minimum sampling number that needs to maintain constant level of quality. Proposed method minimizes load of measure process by brings production quality sophistication and decrease of process badness and lowers measure rate in stable section making perception about problem occurrence quick heightening measure rate at change point occurrence.

• Journal of Korea Foundry Society
• /
• v.37 no.4
• /
• pp.108-114
• /
• 2017

In this study, we investigated the effect of the Si content on the secondary dendrite arm spacing (SDAS) of hypoeutectic Al-Si binary alloys in the range of 4~10 wt% Si. Cooling curves were measured during the solidification of the alloy cast in a step-wise mold. We compared two kinds of solidification time: the first is the total solidification time for both dendritic and eutectic growth, and the second is the solidification time for only dendritic growth. The proportional constant in the relationship between SDAS and cooling rate was estimated, as this constant represents the stability of the cast microstructure. The proportional constant decreased with the Si contents from 4 wt% to 8 wt%, and it remains relatively uniform with up to 10 wt% of Si.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.11 no.6
• /
• pp.928-936
• /
• 1999

An experimental study was performed to investigate characteristics of an inverter driven water-to-water refrigeration system with a variation of compressor frequencies and expansion devices. The frequency of a compressor varied from 30Hz to 75Hz, and performance of the systems applying three different expansion devices such as capillary tube, thermostatic expansion valve(TXV), and electronic expansion valve(EEV) were measured. The load conditions were altered by varying the temperature of the secondary fluid entering condenser and evaporator with a constant flow rate. When the test conditions were deviated from the standard value(rated value), TXV and EEV showed better performance than capillary tube due to optimum control of mass flow rate and superheat. In the present study, it was observed that the variable area expansion device had better performance than constant area expansion device in an inverter refrigeration system due to active control of flow area with a change of compressor frequency and load conditions.

• BMB Reports
• /
• v.39 no.2
• /
• pp.167-170
• /
• 2006

Bovine adenosine deaminase undergoes a nondenaturational conformational change at $29^{\circ}C$ upon heating which is characterized by a large increase in heat capacity. We have determined the transition state thermodynamics of the conformational change using a novel application of differential scanning calorimetry (DSC) which employs very slow scan rates. DSC scans at the conventional, and arbitrary, scan rate of $1^{\circ}C/min$ show no evidence of the transition. Scan rates from 0.030 to $0.20^{\circ}C/min$ reveal the transition indicating it is under kinetic control. The transition temperature $T_t$ and the transition temperature interval ${\Delta}T$ increase with scan rate. A first order rate constant $k_1$ is calculated at each $T_t$ from $k_1\;=\;r_{scan}/{\Delta}T$, where $r_{scan}$ is the scan rate, and an Arrhenius plot is constructed. Standard transition state analysis reveals an activation free energy ${\Delta}G^{\neq}$ of 88.1 kJ/mole and suggests that the conformational change has an unfolding quality that appears to be on the direct path to the physiological-temperature conformer.

• Bulletin of the Korean Chemical Society
• /
• v.31 no.8
• /
• pp.2357-2360
• /
• 2010

Kinetic studies on the pyridinolysis of aryl dithiocyclopentanecarboxyaltes 2 were carried out at $60.0^{\circ}C$ in acetonitrile. In the aminolysis of 2, the $\beta_X$ values were 0.5 - 0.8 with anilines, and there was no breakpoint. However, in the pyridinolysis of 2, biphasic Bronsted plots were obtained, with a change in slope from a large value ($\beta_X{\cong}0.7$) to a small value ($\beta_X{\cong}0.4$) at $pK_{a}^0$ = 5.2. This was attributed to a change in the rate-limiting step from breakdown to the formation of a zwitterionic tetrahedral intermediate, $T^{\pm}$, in the reaction path, with an increase in the basicity of the pyridine nucleophile. An obvious change in the cross-interaction constant ${\rho}_{XZ}$ from a large positive ($\rho_{XZ}$ = +1.02) value to a small negative value (${\rho}_{XZ}$ = -0.17) supports the proposed mechanistic change.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2003.11a
• /
• pp.432-436
• /
• 2003

Geophysical well logging techniques which are useful for delineating permeability of geological formation have been reviewed. A new technique for obtaining permeability using conductivity log technique has been discussed. This conductivity logging technique has been tested by monitoring the conductivity change within the model hole using borehole environment water and incoming-outgoing water of different salinity with constant flow rate by maintaining balance between inflow and outflow. Conductivity variation features depended mainly on flow rate, density contrasts due to salinity and temperature contrasts between fluid within the hole and incoming-outgoing fluid. The results of the experiment show uniform change of fluid conductivity within bore hole with time, and a fairly good correlation between the flow rate and the conductivity change rate. This conductivity logging technique is expected to be an efficient tool for determining permeability.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.461-461
• /
• 2010

For a low dielectric constant inter-metal dielectric application, the low-k SiCOH film with a dielectric constant of 2.8-3.2 has been deposited by plasma-enhanced chemical vapor deposition with decamethylcyclopentasiloxane, cyclohexane, and helium which is carrier gas. In this work, we investigated chemical deposition rate, dielectric constant, characterization of plasma polymer films according to temperature(25C-200C) of substrate and change of component concentration. We measured impedance by using V-I prove during process. From experimental result, deposition rate decrease with increasing temperature. Through real time impedance analysis of chamber, we find corelation between film thickness and impedance by assuming equivalent circuit.

• Journal of the Korean Ceramic Society
• /
• v.36 no.9
• /
• pp.915-922
• /
• 1999

Microwave dielectric properties and far infrared reflectivity spectra of the (Zr0.8Sn0.2)TiO4 ceramics were inves-tigated with the various cooling rate. Dielectric constant was nearly same value while the unloaded Q value was largely affected by cooling rate. The Q.f of 42,140 at 7 GHz was obtained for the specimens with cooling rate of 1$^{\circ}C$/min. The effect of the cooling rate on the change of the ionic the electronic polarization and the intrinsic microwave loss of the specimens were investigated by the infrared reflectivity spectra from 50 to 4000cm-1 which were calculated by Kramers-Kroning analysis and the classical oscillator model. The relative tendency of microwave dielectric properties of the specimens calculated from the relfectivity data were in good agreement with the results by the post resonant method.